The present invention generally pertains to a rearview mirror assembly for a vehicle and to windows (both architectural and vehicular). More particularly, the present invention pertains to a rearview mirror assembly incorporating an electronic device such as a display, light source, and/or light sensor, and to windows having a variable transmittance.
It is desirable to provide electronic devices such as displays, sensors, signal lights, and indicator lights in a rearview mirror assembly of a vehicle. There are several issues with designing a rearview mirror assembly incorporating such an electronic device, particularly when the rearview mirror assembly is an inside mirror assembly. If the electronic device is disposed adjacent the mirror element, it causes the inside rearview mirror assembly to have a larger area, which disadvantageously blocks more of the driver's view through the windshield. To address this problem, electronic devices are provided behind the mirror element so as to transmit or receive light through the mirror element. To allow for light to be transmitted through the mirror element, a portion of the reflective layer of the mirror element is removed to define a window in front of the electronic device. This solution, however, reduces the reflective viewing area of the mirror assembly. Such a window also provides further problems when the reflective layer serves as an electrode for an electro-optic mirror element, such as an electrochromic mirror element. Thus, the window acts to eliminate the electrode across a portion of the electrochromic mirror element thereby causing an objectionable non-uniform coloration of the mirror element when dimmed.
Commonly-assigned U.S. Pat. No. 6,700,692 discloses several solutions for incorporating electronic devices behind an electro-optic mirror element. In particular, this patent discloses the use of a “transflective” layer, which is partially reflective, partially transmissive. Although such a transflective layer is very effective for most forms of electronic devices, the transflective layer tends to block a large percentage of light (passing about 10% of incident light). As a result, the light from a display or light source behind the mirror element is not efficiently transmitted through the transflective layer. This becomes more problematic when a display is provided that displays images of variable brightness during periods of bright daylight. This is because the reflectivity of the transflective layer is still rather high, and therefore, there is large light loss going through transflective layer producing poorer contrast. The above '692 patent further discloses an embodiment whereby slit-like, parallel apertures are etched in the reflective layer in front of a compass display and/or in front of turn signal indicator lights. Such apertures are often relatively large and few in number.
Recently, there has been a strong interest to provide a high resolution video-type display in or around the position of an inside rearview mirror assembly. One such application is backup control/vision on large vehicles such as sport utility vehicles (SUVs) or minivans where a clear view of what is behind is blocked by the car interior, seats, headrests, or other items. Positioning a camera on or near the back of the vehicle with the image displayed on or near the rearview mirror can aid the driver in backing up safely. This image could be displayed only when the vehicle is in reverse or it could be used to supplement or replace the mirror when driving. In which case, it is desirable to have a mirror available as a back up for the camera/display system in case it fails.
Rearview mirrors have been proposed that include a video display that pulls down from the mirror body for use in back up situations. Again, this is disadvantageous in that the video display blocks the driver's view to the front of the vehicle. Further, the video display size is limited. Additionally, the driver must manually pull down the display, and the display is in a position that is vulnerable to damage by passengers or objects.
Accordingly, there exists the need for a rearview mirror assembly incorporating an electronic device where the electronic device may transmit or receive light efficiently through the mirror element.
Variable transmission windows have been proposed for architectural windows and skylights and for sunroofs and windows for vehicles, including automobiles, trucks, recreational vehicles and trailers, airplanes, trains, and boats. One form of variable transmission window that has been proposed utilizes an electrochromic element that changes from a colorless state to a colored state in response to an applied voltage. Such electrochromic elements thus vary the transmittance of the window by changing color and absorbing light that is not to be transmitted. Such electrochromic windows are disclosed in U.S. Pat. Nos. 6,239,898, 6,594,065, 6,407,847, 6,594,067, 6,671,080, 6,842,276, 6,567,708, 6,597,489, 6,045,643, and 5,805,330. Electrochromic windows function suitably for most applications. However, electrochromic windows do not respond instantaneously to an applied voltage and absorb and thus radiate heat.
Accordingly, there exists the need for a variable transmission window that more quickly responds to an applied voltage and that varies transmission by blocking both visible and infrared light without absorbing light and thus generating heat inside the building.